It would help a lot if you all would give a location. It is also kind of hard without a flower. It is obviously a legume (Fabaceae). Probably Mimosa subfamily. If you are in Australia, I would guess maybe an Acacia??

This plant is on Indian soil. I ask this because this plant grew very quick on a fly-ash dump. It grew itself naturally and quite dense as can be seen in the pics. I am interested to learn if there are any specific properties in the fly ash that were so favorable for this plant.

I don't know Asian plants (sorry). You might try ID Please on Flickr: http://www.flickr.com/groups/idplease/ A basic account is free on Flickr. Flickr has a lot of Asian members and they would probably recognize your plant quickly.

The reason it is probably on the fly ash is that there is no Nitrogen in the ash and the only plants that can grow on the Nitrogen free environment are nitrogen fixers like legumes. Since it is an obviously an invasive plant, probably someone on Flickr would recognize it pretty quickly.